Optical fiber tape core and production method therefor

ABSTRACT

An optical fiber tape core comprises an optical fiber core assembly and a coating layer formed of silicone rubber and arranged on at least one side of the optical fiber core assembly. In the optical fiber core assembly, plural optical fiber cores two-dimensionally are arranged in parallel with each other. The silicone rubber which forms the coating layer has a hardness of from 20 to 90 and a tensile strength of from 15 to 80 kgf/cm 2 .

This application is a 371 of PCT/JP03/08909 filed on Jul. 14, 2003.

TECHNICAL FIELD

This invention relates to optical fiber tape cores in each of whichplural optical fiber cores two-dimensionally arranged in parallel witheach other are united together in the form of a tape with a coatinglayer, and also to their fabrication process.

BACKGROUND ART

Optical fiber tape cores each of which is formed of a bundle of pluraloptical fiber cores united together are known for many years. Owing tothe merit that a number of optical fibers can be connected all together,these optical fiber tape cores are widely used as optical transmissionmedia in optical communications systems as a result of the rapidintroduction of optical fiber cables in subscribers' systems in recentyears.

An optical fiber tape core is required to have higher separability intosingle cores and higher strength, and active research and developmentwork is under way in various companies. To provide optical fiber coreswith both strength and separability into single cores, it is the commonpractice to form a coating layer in a two-layer construction—one being aprimary coating layer uniting plural optical fiber cores together andthe other a secondary coating layer uniting together such multi-coreunits covered with such primary coating layers, respectively—and to formthe primary and secondary coating layers with UV curable resinsdifferent in strength and hardness.

In general, optical fiber tape cores coated with such UV curable resinsare fabricated using acrylic materials. The resulting optical fiber tapecores are, however, accompanied by a problem in that they are notsufficient in hardness, durability and flexibility and tend to becomeloose or break, for example, when twisted. Concerning flexibility, onthe other hand, these optical fiber tape cores also involve a problem inthat they are extremely weak to bending in the direction of the coresand becomes loose or break although they have durability to folding.

Further, optical fiber tape cores coated with general UV curable resinsare also accompanied by a further problem in that they are poor in shaperestorability due to their plasticity attributable to the materials and,when wound on bobbins or the like upon storage, they continue to retaina wound shape, in other words, they develop curling and in actual work,for example, upon conducting connection to connectors or the like orperforming installation work, this retention of a wound shape (curling)makes it difficult to handle them, resulting in poor workability.

Turning now to a process for the fabrication of optical fiber tapecores, the conventional fabrication of an optical fiber tape core hasbeen conducted generally by the facilities illustrated in FIG. 22.Described specifically, an optical fiber tape core is fabricated byguiding plural optical fiber cores 2 a-2 h from a core feeder 16 to acore aligner 17 to align the individual optical fiber cores in parallelwith each other along a line, introducing the thus-aligned individualoptical fiber cores into a coating jig 18, coating the optical fibercores all together around themselves with a coating material whilefilling the coating jig 18 with the coating material, feeding out thecoated optical fiber cores through a hole of the coating jig 18, andthen curing the coating material by a curing means 19 such as a UVirradiation unit. A typical coating jig is illustrated in FIG. 23. Thecoating jig 18 is constructed of an optical fiber feed-in hole 18 athrough which the optical fibers 2 a-2 h are inserted, a coatingmaterial reservoir 18 b in which a coating material is filled, and anoptical fiber feed-out hole 18 c through which the optical fiber coresare fed out.

According to this process, however, it is necessary to keep the interiorof the coating jig always filled with the coating material, leading to aproblem that the material is wasted. This problem involves anotherproblem in that to change the thickness and/or width of an optical fibertape, a new coating jig equipped with a different hole for feedingoptical fiber cores therethrough is needed, thereby making it difficultto readily change the thickness and/or width of the optical fiber tape.

In the above described process, it is also necessary to feed pluraloptical fiber cores, which are before their formation into a tape andare single cores in a loose state, through the aligner 17 while aligningthem with each other and then to insert them into the very small holes(18 a and 18 c) of the coating jig 18. This setting of the optical fibercores is troublesome and time-consuming, leading to a reduction in workefficiency. With respect to a demand for the fabrication of ashort-distance optical fiber tape core or the formation of an opticalfiber tape core into a tape only at a necessary position, thefabrication facilities are difficult to meet such a demand because thedistance from the core feeder 16 to the curing unit 19 is tong andfabrication conditions such as the coat thickness do not become constantshortly after an initiation of fabrication.

When fabricating a short-distance optical fiber tape core, forming anoptical fiber tape core into a tape only at a necessary position orreinforcing an optical fiber tape core only at a part thereof, it isstrongly required to provide the optical fiber tape core with a thickercoating layer, a wider coating layer or the like especially from thestandpoint of protection of the optical fibers to be wired within asystem. However, the above-described conventional process can by nomeans meet or is difficult to meet these requirements.

From the standpoint of protecting optical fibers drawn out of opticalconnectors or an optical component, it is strongly required to form theminto a tape. The above-described process is, however, accompanied by aproblem in that the tape formation can be hardly effected. Theabove-described process involves a further problem in that, when opticalfibers are wired in a very narrow place, it cannot effect the tapeformation.

The present invention has been completed to resolve such problems of theconventional technology as described above. Specifically, an object ofthe present invention is to provide an optical fiber tape core, whichhas excellent strength and good flexibility and hardly retains a woundshape (curling).

Another object of the present invention is to provide a process for thefabrication of an optical fiber tape core, which can coat plural opticalfiber cores all together in a simple manner. A further object of thepresent invention is to provide a process for the fabrication of anoptical fiber tape core, which can feed a coating material to opticalfiber cores only as much as required, can feed a coating material evenwhen the area to be coated extends over a short distance or is partial,can feed a coating material even when optical fiber cores to be coatedare wired in a very narrow place, or can feed a coating material tooptical fiber cores to form it into a tape while controlling thethickness and/or width of the coating of the tape. A still furtherobject of the present invention is to provide a process for thefabrication of an optical fiber tape core, which can simplify thesetting of plural optical fiber cores, can apply a coating over a shortdistance or on a partial area without wasting a coating material, or canalso form into a tape plural optical fiber cores provided at one ends orboth ends thereof with optical components such as optical connectors.

DISCLOSURE OF THE INVENTION

An optical fiber tape core according to the present invention comprisesan optical fiber core assembly with plural optical fiber corestwo-dimensionally arranged in parallel with each other and a coatinglayer formed of silicone rubber and arranged on at least one side of theoptical fiber core assembly. In the optical fiber tape core according tothe present invention, the silicone rubber forming the coating layer canpreferably have a hardness of from 20 to 90 and a tensile strength offrom 15 to 80 kgf/cm².

In the present invention, the optical fiber core assembly may beprovided on both upper and lower sides thereof with coating layersformed of the silicone rubber, and may also be provided on side wallsthereof with additional coating layers formed of the silicone rubber.These coating layers can bring about further improvements in strength.

The term “hardness” as used herein means “durometer hardness” asmeasured following the procedure prescribed in JIS K6253. Specifically,the term “hardness” means a value measured by preparing a specimen 6 mmthick of silicone rubber, pressing a needle of a Type A durometeragainst the specimen without any impact from a point right above anupper surface of the specimen, and reading graduations. A durometer is atesting machine for determining a hardness from a penetration depth of aneedle when the needle is pressed by means of a spring.

On the other hand, the term “tensile strength” as used herein means“tensile strength at break” as measured following the procedureprescribed in JIS K6251. Specifically, the term “tensile strength” meansa value [kgf/cm²] calculated by preparing a JIS No. 2 dumbbell-shapedspecimen about 2 mm thick of silicone rubber, pulling the specimen at apulling speed of 500 mm/min, and dividing a load value, when thespecimen was broken, by a cross-sectional area of the specimen.

The optical fiber tape core according to the present invention can alsobe characterized in the use of a silicone rubber material, which has theabove-described hardness and tensile strength, as a coating material,and owing to the excellent shape restorability of the silicone rubber,is extremely good in workability and handling without developing curlingor retaining a wound shape even when wound on a bobbin or the like.

A process according to the present invention for the fabrication of anoptical fiber tape core is a process for fabricating the optical fibertape core by coating plural optical fiber cores all together, and in afirst embodiment thereof, comprises bringing at least one nozzle closeto the surfaces of the plural optical fibers aligned in parallel witheach other on a two-dimensional flat surface; and then, while deliveringsilicone rubber from the nozzle, causing the nozzle to undergo arelative movement in a direction of axes of the optical fibers such thatthe plural optical fibers are coated all together to form a coatinglayer.

The process according to the present invention for the fabrication ofthe optical fiber tape core comprises, in a second embodiment thereof,applying silicone rubber onto the plural optical fiber cores arranged ona two-dimensional flat surface; and with a shaping jig having a shapinggroove and being arranged such that the plural optical fiber cores arelocated in the shaping groove or are located underneath in proximity ofthe shaping groove, causing the forming jig to undergo a relativemovement in a direction of axes of the optical fiber cores such that thesilicone rubber is shaped to form a coating layer.

The process according to the present invention for the fabrication ofthe optical fiber tape core comprises, in a third embodiment thereof,arranging the optical fiber cores on a two-dimensional flat surface; andwith a shaping jig having a shaping groove provided with a through-holefor feeding silicone rubber and being arranged such that the pluraloptical fiber cores are located in the shaping groove or are locatedunderneath in proximity of the shaping groove, causing the shaping jigto undergo a relative movement in a direction of axes of the opticalfiber cores such that with the silicone rubber fed into the shapinggroove from the through-hole, the optical fiber cores are coated andshaped to form a coating layer.

The process according to the present invention for the fabrication ofthe optical fiber tape core comprises, in a fourth embodiment thereof,mounting the optical fiber cores in alignment with each other on atwo-dimensional flat surface; applying silicone rubber onto thetwo-dimensional flat surface such that the two-dimensional surface withthe plural optical fiber cores mounted therein is coated with thesilicone rubber to form a coating layer; and peeling off the pluraloptical fiber cores from the two-dimensional flat surface to separate,from the coating layer on the two-dimensional flat surface, only a partthereof located on the optical fiber cores.

In these first to fourth embodiments of the present invention, it ispreferred to use silicone rubber having a hardness of from 20 to 90 anda tensile strength of from 15 to 80 kgf/cm².

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partly cut-away, schematic plan view illustrating oneexample of preferred embodiments of the optical fiber tape coreaccording to the present invention.

FIG. 2 shows schematic cross-sectional views of optical fiber tapes eachof which is of such a form that a coating layer is arranged on one sideof an optical fiber core assembly.

FIG. 3 shows schematic cross-sectional views of optical fiber tapes eachof which is of such a form that coating layers are arranged on bothsides of an optical fiber core assembly.

FIG. 4 shows flow diagrams illustrating a first embodiment of theprocess according to the present invention for the fabrication of anoptical fiber tape core.

FIG. 5 is a perspective view of one example of a nozzle useful in theprocess according to the present invention for the fabrication of theoptical fiber tape core.

FIG. 6 shows side views of various nozzles useful in the presentinvention.

FIG. 7 illustrates another example of the first embodiment of theprocess according to the present invention for the fabrication of theoptical fiber tape core, in which FIG. 7( a) is a side view and FIG. 7(b) is a front view.

FIG. 8 shows flow diagrams illustrating a further example of the firstembodiment of the process according to the present invention for thefabrication of the optical fiber tape core.

FIG. 9 shows flow diagrams illustrating a second embodiment of theprocess according to the present invention for the fabrication of theoptical fiber tape core.

FIG. 10 shows flow diagrams illustrating a third embodiment of theprocess according to the present invention for the fabrication of theoptical fiber tape core.

FIG. 11 shows flow diagrams illustrating another example of the thirdembodiment of the process according to the present invention for thefabrication of the optical fiber tape core.

FIG. 12 shows perspective views of shaping jigs usable in FIG. 11.

FIG. 13 shows flow diagrams illustrating a further example of the thirdembodiment of the process according to the present invention for thefabrication of the optical fiber tape core.

FIG. 14 shows flow diagrams illustrating an example of a fourthembodiment of the process according to the present invention for thefabrication of the optical fiber tape core.

FIG. 15 shows flow diagrams illustrating another example of the fourthembodiment of the process according to the present invention for thefabrication of the optical fiber tape core.

FIG. 16 shows flow diagrams illustrating a further example of the fourthembodiment of the process according to the present invention for thefabrication of the optical fiber tape core.

FIG. 17 shows flow diagrams illustrating a still further example of thefourth embodiment of the process according to the present invention forthe fabrication of the optical fiber tape core.

FIG. 18 shows flow diagrams for illustrating the fabrication of anoptical fiber tape core in Example 7.

FIG. 19 shows flow diagrams for illustrating the fabrication of anoptical fiber tape core in Example 11.

FIG. 20 shows flow diagrams for illustrating the fabrication of anoptical fiber tape core in Example 12.

FIG. 21 shows flow diagrams for illustrating the fabrication of anoptical fiber tape core in Example 13.

FIG. 22 is a flow diagram for illustrating the conventional fabricationof an optical fiber tape core.

FIG. 23 shows a perspective view (a) and cross-sectional view (b) of aconventional coating (shaping) jig.

LEGEND

1 . . . optical fiber tape core, 2,2 a-2 h . . . optical fiber core, 3 .. . coating material, 3 a,3 b . . . coating layer, 4,4′,4″ . . . nozzle,4 a . . . opening, 5 . . . substrate, 6 . . . adhesive tape, 7 . . .shaping jig, 7 a . . . shaping groove, 7 b . . . through-hole, 7 f . . .leg, 8 . . . pipe, 9 . . . 1—axis controlled robot, 10 . . . flatsubstrate, 11 . . . ball screw shaft, 12 . . . movable unit, 13 . . .coating material feeder, 14 . . . drive motor, 15 . . . journal bearing,A . . . coating start position, B . . . coating end position.

BEST MODES FOR CARRYING OUT THE INVENTION

The embodiments of the present invention will hereinafter be describedin detail with reference to the drawings.

In FIG. 1 through FIG. 3, each optical fiber tape core 1 is providedwith eight optical fiber cores 2 a-2 h arranged in parallel with eachother, and a coating layer 3 a or 3 b formed of silicone rubber of theabove-described properties is arranged in spaces between the opticalfiber cores and on upper sides or upper and lower sides of the opticalfiber cores.

In the present invention, it is only necessary for the coating layer 3 athat as illustrated in FIG. 2( a) through FIG. 2( d), it is formed onone side of a two-dimensional assembly of the optical fiber coresarranged in parallel with each other. The coating layer 3 a may protrudesomewhat onto side walls of the two-dimensional assembly. It is onlynecessary for the optical fiber cores that they are arrangedtwo-dimensionally in parallel with each other, and no problem orinconvenience arises even when some spaces are left between the adjacentoptical fiber cores. These spaces can be either equal to or differentfrom each other. Further, the spaces may be filled with silicone rubber.

As illustrated in FIG. 3( a) through 3(d), coating layers can bearranged on both sides of a two-dimensional assembly of optical fibercores arranged in parallel with each other. In this case, the eightoptical fiber cores 2 a-2 h arranged in parallel with each other arecoated with a coating layer 3 b of silicone rubber such that they arecovered at outer peripheries thereof. The coating layer 3 b may protrudesomewhat onto side walls of the two-dimensional assembly. It is onlynecessary for the optical fiber cores that they are arranged in parallelwith each other, and no problem or inconvenience arises even when somespaces are left between the adjacent optical fiber cores. Further, thespaces may be filled with silicone rubber.

The silicone rubber forming the coating layer of the optical fiber tapecore according to the present invention may preferably have a hardnessof from 20 to 90 and a tensile strength of from 15 to 80 kgf/cm². Morepreferred silicone rubber has a hardness of from 25 to 75 and a tensilestrength of from 15 to 60 kgf/cm². Still more preferred silicone rubberhas a hardness of from 30 to 65 and a tensile strength of from 15 to 50kgf/cm².

Silicone rubber the hardness and tensile strength of which are lowerthan 20 and lower than 15 kgf/cm², respectively, cannot provide theresulting optical fiber tape core with sufficient strength againstlateral pressures, twisting and the like, so that during fabrication orinstallation, the optical fiber tape cores are susceptible to breakageeven under a small strain. If the hardness is higher than 90 and thetensile strength is higher than 80 kgf/cm², on the other hand, theresulting optical fiber tape core is sufficient neither in flexibilitynor in separability into single cores.

In the present invention, no particular limitation is imposed on thesilicone rubber insofar as its hardness and tensile strength fall withinthe above-described corresponding ranges. The addition reaction curingtype, the condensation reaction curing type, and the vulcanizable typeare all usable. Among these, silicone rubber of the addition reactioncuring type or the condensation reaction curing type is preferred forits production of less byproducts and its good workability.

The thickness of the optical fiber tape core can be selectivelydetermined as needed in accordance with its application purpose. Ingeneral, however, the thickness, including that of optical fiber cores,can be set within a range of from 300 μm to 480 μm, preferably from 330μm to 430 μm, more preferably from 350 μm to 410 μm when the employedoptical fiber cores have a thickness of 250 μm. Further, the width ofthe optical fiber tape core can also be selectively determined as neededin accordance with its application purpose. In general, however, thewidth, including that of optical fiber cores, can be set within a rangeof form 2,000 μm to 2,300 μm, preferably from 2,050 μm to 2,250 μm wheneight optical fiber cores having a diameter of 250 μm are arranged inparallel with each other.

In addition, no particular limitation is imposed on the number ofoptical fiber cores in the optical fiber tape core according to thepresent invention, so that the optical fiber tape core can be a 2-coreor 12-core optical-fiber tape core in addition to a 4-core optical-fibertape core equipped with four optical fiber cores or an 8-coreoptical-fiber tape core equipped with eight optical fiber cores.

The optical fiber tape core according to the present invention, whichhas such a construction as described above, has sufficiently highstrength and excellent flexibility and also sufficient anti-curlingproperty, so that its optical fiber cores neither undergo breakage nordevelop curling when handled upon connecting them to connectors orduring installation work. Accordingly, the optical fiber tape coreaccording to the present invention has high reliability and assuresimprovements in the safety and efficiency of work. Because the opticalfiber tape core according to the present invention has excellentseparability into single cores, the work to separate the optical fibercores from each other can be performed easily without failure.

The optical fiber tape core according to the present invention isfabricated using silicone rubber as a coating material. It is preferredto fabricate the optical fiber tape core in accordance with theabove-described first to fourth embodiments of the present invention.

Firstly, the first embodiment of the process of the present inventionfor the fabrication of an optical fiber tape core will be described withreference to the drawings. The first embodiment of the process for thefabrication of the optical fiber tape core firstly comprises, asillustrated in FIG. 4, moving a nozzle 4 to a coating start position Aand to a proximity of the surfaces of plural optical fiber cores 2 a-2 daligned in parallel with each other on a two-dimensional flat surface(FIG. 4( a)). Next, the nozzle 4 is moved in a direction of axes of theoptical fibers while delivering a coating material 3 from an opening 4 ain a tip of the nozzle (FIG. 4( b)). After the nozzle 4 is moved to acoating end position B, the delivery of the coating material from theopening in the tip of the nozzle is stopped to finish the coating of thecoating material to the optical fibers (FIG. 4( c)). An optical fibertape core of a uniform shape can be fabricated by controlling the movingspeed of the nozzle 4 and the delivery rate of the coating material topredetermined values during the above-described operation. By changingthe moving speed of the nozzle and the delivery rate during the coating,it is also possible to change the shape of the coating. By making theoptical fiber tape core thicker at a part thereof, the optical fibertape core can be improved in mechanical strength. By controlling thedistance of movement, it is possible to fabricate an optical fiber tapecore of a desired length. Accordingly, an optical fiber tape core can beformed into a tape over a predetermined length thereof. Subsequently,the coating material so applied may be dried or cured as needed.

In the present invention, the movement of the nozzle 4 can be effectedby using any means, for example, can be effected either manually orautomatically without any problem or inconvenience. It is, however,preferred to use such a system that permits control of the moving speedand also permits a movement at a constant speed and a stop. It is to benoted that the movement of the nozzle in the present invention is onlyrequired to be relative and either the nozzle or the optical fiber corescan be moved forwards each other, respectively. As the coating materialis applied by the nozzle in the present invention, even optical fibercores wired in a very narrow space can be formed into a tape insofar asthere is a space sufficient to permit an insertion of the nozzle.

The nozzle for use in the present invention may preferably be in atubular shape as depicted in FIG. 5. The material of the nozzle 4 maypreferably be, but not particularly limited to, a material which doesnot corrode or has low reactivity to chemical substances, e.g. stainlesssteel, fluorinated resin or the like. The nozzle is connected to thecoating material feeder. For the feeding of the coating material fromthe coating material feeder, any means can be used, for example, thefeeding can be either manual or automatic. It is, however, preferred topermit control of the feed rate of the coating material. The opening 4 ain the tip of the nozzle can be of any shape, for example, can becircular, elliptic, rectangular or so. Any modifications can be appliedto the nozzle, for example, a blade-like part can be attached to the tipof the nozzle. Further, no particular limitation is imposed on thediameter of the opening insofar as the coating material can be deliveredonto the optical fiber cores.

In the present invention, the nozzle for use in applying the coatingmaterial is not necessarily limited to a single nozzle, but can be inthe form of plural nozzles. FIG. 6(a) shows by way of example theinclusion of two nozzles (4′,4″). As illustrated in FIG. 6( b), thenozzle can be in the form of plural nozzles integrated together or inthe form of a single nozzle provided with plural openings. As depictedin FIG. 6( c), the nozzle can be one arranged with an inclination to thetwo-dimensional flat surface.

In another example of the first embodiment of the fabrication processaccording to the present invention as illustrated in FIG. 7, a coatingmaterial is applied, to both sides of optical fiber cores aligned inparallel with each other which is different from the example of FIG. 4.Described specifically, nozzles 4 and 4′ are brought close to both ofthe upper and lower sides of the plural optical fiber cores aligned inparallel with each other, and while delivering a coating material 3 fromthe openings in the tips of the respective nozzles, the nozzles are bothmoved in the direction of the axes of the optical fibers. As a result,the plural optical fiber cores are coated with the silicone rubber onthe both sides thereof. It is to be noted that, although the opticalfiber cores are coated on both of the upper and lower sides thereof inFIG. 7, the optical fiber cores can be arranged in parallel with eachother in a vertical direction, that is, in an up-and-down direction andcan be coated on both left and right sides thereof.

In a further example of the first embodiment shown in FIG. 8, a coatingmaterial for the rear side of optical fibers is applied beforehand inthe form of a two-dimensional flat surface on a releasing substrate toform a coating layer 3 a (FIG. 8( a)). After plural optical fiber cores2 a-2 h are aligned and held in place on the coating layer 3 a (FIG. 8(b)), a coating material 3 is applied by the above-described method froma nozzle 4 onto the surfaces of the optical fiber cores aligned inparallel with each other to obtain an optical fiber tape core coated onboth sides (FIG. 8( c)).

When applying the coating material to the optical fiber cores, theposition of the nozzle relative to the plural optical fiber cores can beset so as to permit the application of the coating material onto all theoptical fiber cores. It is to be noted that the clearance between thenozzle and the optical fiber cores can be selectively determined asneeded to form the coating layer with desired shape and thickness. Inthe present invention, it is also possible to change the coatingconditions in the course of the coating operation. Describedspecifically, the moving speed of the nozzle, the clearance between thenozzle and the optical fiber cores and the delivery rate of the coatingmaterial can be changed as needed, and therefore, can be selectivelydetermined, for example, depending on the application purpose and thesystem construction. The stop of the delivery of the coating materialfrom the nozzle at the coating end position and the movement of thenozzle can be selectively determined depending on the shape of the tapeand the application purpose. For example, the delivery of the coatingmaterial from the moving nozzle can be stopped at the coating endposition, and the nozzle can then be moved further such that the nozzlepasses beyond the coating end position.

According to the above-described first embodiment of the process of thepresent invention for the fabrication of an optical fiber tape core, thecoating material can be applied only as much as needed owing to the useof the nozzle so that the optical fiber tape core can be fabricatedwithout waste of material. As the moving speed and distance of thenozzle can be controlled, it is also possible to feed the coatingmaterial to optical fiber cores even at parts thereof or over a shortdistance, and moreover, it is also possible to coat optical fiber coresall together with the coating material over a desired distance withdesired tape width and thickness. Accordingly, optical fiber cores canbe formed into a tape in order to improve mechanical strength, handlingworkability and the like. In addition, the use of the nozzle which is avery small coating jig makes it possible to coat plural optical fibercores all together even if they are those drawn out of an opticalcomponent or optical connectors or those wired in a narrow place.

The second embodiment of the process of the present invention for thefabrication of an optical fiber tape core will next be described withreference to the drawings. The second embodiment of the process for thefabrication of the optical fiber tape core firstly comprises, asillustrated in FIG. 9, arranging plural optical fiber cores (fouroptical fiber cores in the diagrams) 2 a-2 d in alignment with eachother on a two-dimensional flat surface and fixing them at end portionsthereof with an adhesive tape 6. A coating material 3 is then appliedbeforehand over the optical fiber cores (FIG. 9( a)). From a point abovethe plural optical fiber cores 2 a-2 d, a shaping jig 7 provided on abottom wall thereof with a shaping groove 7 a is next caused to descend,and is mounted on the flat surface such that the plural optical fibercores are arranged in the shaping groove of the shaping jig (FIG. 9(b)). The shaping jig 7 is then moved in the direction of the axes of theoptical fiber cores. As an alternative, the optical fiber cores may bemoved instead of the shaping jig. It is to be noted that the opticalfiber cores may be arranged underneath in close proximity of the shapinggroove of the shaping jig 7 rather than being arranged in the shapinggroove, and the shaping jig 7 may then be moved in the direction of theaxes of the optical fiber cores. By this operation, the shape of theresulting silicone rubber coating layer is determined by the shapinggroove of the shaping jig, and the coating layer is thus formed withshape forming from the coating start position A (FIG. 9( c)). Theshaping jig is moved continuously to the coating end position B, therebycompleting the shaping of the silicone rubber coating layer (FIG. 9(d)). Subsequently, the thus-shaped silicone rubber coating layer may bedried or cured as needed.

According to the above-described second embodiment, the setting of theoptical fibers at the time of the initiation of the fabrication of theoptical fiber tape core is completed by positioning the plural opticalfiber cores on the flat surface in the shaping groove of the shaping jigor on the flat surface underneath the shaping groove of the shaping jigheld in a proximity of the flat surface. The setting of the opticalfibers for performing their formation into a tape can, therefore, beconducted very easily in a short time. Because the shaping of thecoating material is effected by simply moving the shaping jig of thesimple construction, which is provided only with the shaping groove, inthe direction of the axes of the optical fiber cores, the formation intothe tape can be conducted very easily.

The third embodiment of the process for the fabrication of an opticalfiber tape core will next be described with reference to the drawings.As shown in FIG. 10, the third embodiment firstly comprises, in asimilar manner as in the above-described embodiment depicted in FIG. 9,arranging plural optical fiber cores (four optical fiber cores in thediagrams) 2 a-2 d in alignment with each other on a two-dimensional flatsurface, causing a shaping jig 7, which is provided on a bottom wallthereof with a shaping groove 7 a and is also provided with athrough-hole 7 b for feeding a coating material, to descend from a pointabove the plural optical fiber cores, and mounting the shaping jig onthe flat surface such that the plural optical fiber cores are arrangedin the shaping groove of the shaping jig (FIG. 10( a)). It is to benoted that as an alternative, the optical fiber cores may be arrangedunderneath in close proximity of the shaping groove of the shaping jig 7rather than being arranged in the shaping groove. The shaping jig 7 isthen moved in the direction of the axes of the optical fiber cores. Whenthe shaping jig has reached a predetermined position, specifically acoating start position A, the coating material is fed from anunillustrated coating material feeder to a through-hole 7 b via a pipe 8and the delivery of the coating material is started, and the shaping jigis moved while feeding the coating material 3 (FIG. 10( b)). When theshaping jig has reached a coating end position B, the delivery of thecoating material is stopped to complete the coating of the optical fibercores and the shaping of the resulting coating layer (FIG. 10( c)). Itis to be noted that the optical fiber cores may be moved although theshaping jig was moved in the above-described procedure. Subsequently,the thus-shaped silicone rubber coating layer may be dried or cured asdesired.

FIG. 11 shows flow diagrams of another example of the third embodimentof the process of the present invention for the fabrication of anoptical fiber tape core. In this example, coating is conducted whilebringing unaligned optical fiber cores into alignment with each other.Plural optical fiber cores, specifically optical fiber cores 2 a-2 d,which are arranged on a two-dimensional flat surface but are not inalignment with each other, are rendered flush with each other at oneends thereof and are held in place with an adhesive tape 6, and on thecore portions rendered flush with each other, a shaping jig 7 is mounted(FIG. 11( a)). When the shaping jig has reached a coating start positionA by moving it, the coating material is fed to the shaping jig 7 via apipe 8 to initiate coating and shaping. With the movement of the shapingjig, the unaligned optical fiber cores are brought into alignment witheach other by a shaping groove 7 a of the shaping jig, said shapinggroove being rectangular in cross-section, and the coating material isfed on the optical fiber cores to perform coating and shaping (FIG. 11(b)). When the shaping jig has reached a coating end position B, thedelivery of the coating material is stopped to complete the coating ofthe optical fiber cores and the shaping of the resulting coating layer(FIG. 11( c)). Subsequently, the thus-shaped silicone rubber coatinglayer may be dried or cured as desired.

Examples of the shaping jig 7 employed in the above-described procedurecan include those of the constructions shown in FIG. 12( a) and FIG. 12(b), respectively. Different from the shaping jig shown in FIG. 10, eachof the shaping jigs shown in FIG. 12( a) and FIG. 12( b) is providedwith a through-hole 7 b at a substantially central part of the shapingjig as viewed in the direction of the length thereof, and its shapinggroove 7 b is rectangular in cross-sectional shape. With any one ofthese shaping jigs, it is hence possible to bring optical fiber coresinto alignment with each other. Incidentally, the term “alignment” asused herein means to put optical fiber cores together side by side intoa state ready to conduct the coating of a coating material byregulating, prior to the coating, movements of the optical fiber coressuch that their coating with the coating material becomes feasible. Asillustrated in FIG. 12( a), the shaping jig for use in this procedureis, therefore, provided with a function to regulate the movements of theoptical fibers by a portion of the shaping groove having the rectangularshape in cross-section, said portion being located forward of thethrough-hole through which the coating material is delivered, such thatthe optical fibers are put together side by side. The shaping jigillustrated in FIG. 12( b), on the other hand, has two legs 7 f,7 f atan interval either equal to or slightly wider than the width of theshaping groove, and has a function to put optical fibers together sideby side.

FIG. 13 shows flow diagrams of a further example of the thirdembodiment, and illustrates a procedure to fabricate an optical fibertape core of a construction coated on both sides thereof. Describedspecifically, a coating material for the rear side is applied on atwo-dimensional flat surface to form a coating layer 3 a (FIG. 13( a)),and on the coating layer, plural optical fiber cores (four optical fibercores in the drawing) 2 a-2 d are arranged in alignment with each other(FIG. 13( b)). Subsequently, a shaping jig 7 provided with athrough-hole is mounted such that the optical fiber cores 2 a-2 d arereceived in a shaping groove of the shaping jig (FIG. 14( c)). The samecoating material is fed to the shaping jig through a pipe 8 to performcoating and shaping, whereby an optical fiber tape core is formed withboth sides thereof coated with the coating layer 3 b formed of siliconerubber (FIG. 13( d)).

As the coating material is fed to the shaping groove of the shaping jigin the above-described third embodiment, the coating and shaping of thecoating material can be conducted in a single step by the single shapingjig. By controlling the feed position and feed rate of the coatingmaterial from a coating material feeder, it is also possible to avoidany over-feeding of the coating material to make an improvement in thematerial yield of the coating material and further, to set the width andthickness of the resulting tape as desired. By controlling the distanceof a relative movement of the shaping jig, it is also possible to formoptical fiber cores into a tape over a short distance thereof or to formparts of optical fiber cores into a tape at a desired position. It is tobe noted that the term “relative” as used herein means that either theshaping jig or the arranged optical fiber cores can be moved forwardseach other, respectively.

For use in the fabrication process of the second or third embodiment,any shaping jig can be selected depending upon the application object orthe like of the optical fiber tape core insofar as it is equipped with ashaping groove. No particular limitation is imposed on thecross-sectional shape of the shaping jig because it can be selected asneeded depending upon the shape of the applied coating material and itsspecification, but for example, a semielliptic, rectangular orsemicircular cross-sectional shape or the like can be mentioned. Theshaping jig can be of either a single-piece, unitary structure made of asingle material or a structure of discrete parts assembled together.Further, the height, width and length of the shaping groove of theshaping jig can be selectively set as desired. The height is notrequired to be constant in the shaping jig, and may vary as needed. Inaddition, no particular limitation is imposed on the position of theshaping groove in the direction of the width of the shaping jig, and theshaping groove can be arranged at any position insofar as it is locatedwithin the width of the shaping jig. Furthermore, it is not necessary tolimit to one (1) as the number of shaping groove(s) to be arranged in ashaping jig. For example, a single shaping jig can be provided withplural shaping grooves to fabricate plural optical fiber tape cores atonce. A shaping groove of a shaping jig can be chamfered off at anupstream end portion thereof to facilitate the introduction of opticalfiber cores into the shaping groove. As described above, it is alsopossible to use a shaping jig of the construction that two legs arearranged at an interval either equal to or wider than the width of theshaping groove to regulate optical fibers into alignment with each other(FIG. 12( b)) or a shaping jig of a construction that the width of itsshaping groove is rendered somewhat wider into a tapered shape on thefeed-in side of optical fibers.

No particular limitation is imposed on the size of the shaping jig, andthe size can be selectively set as desired, for example, depending uponthe number or the like of optical fiber tape cores. No particularlimitation is imposed on its shape either. For example, a shape such asa quonset-shaped or parallelepipedal shape can be mentioned. Moreover,no particular limitation is imposed on the material which makes up theshaping jig, but preferred examples include materials having smallfriction coefficients such as polyacetal resins, materials having goodmechanical properties such as materials resistant to thermaldeformations, none-corrosive materials such as stainless steel,trifluoroethylene resin and tetrafluoroethylene resin, and materialshaving low resistance to chemical substances and solvents.

The shape of the through-hole arranged in the shaping jig to feed thecoating material can be selectively set depending upon its applicationpurpose, and therefore, the through-hole can have any shape.Illustrative are circular shape, elliptic shape, and rectangular shape.It is unnecessary to arrange only one through-hole, and pluralthrough-holes may be arranged. No particular limitation is imposed onthe size of the through-hole insofar as it can feed the coating materialand can apply the coating material onto the optical fiber cores.Further, the through-hole can be located at any position insofar as itextends to the shaping groove. Moreover, the direction of thethrough-hole is not required to be perpendicular to the flat surface,and may have an inclination with respect to the flat surface.

To bring the optical fiber cores into alignment with each other by theshaping jig, the shaping jig is required to have, at a part thereofforward of the through-hole through which the coating material is fed, aconstruction that can regulate movements of the optical fiber cores andcan put the optical fiber cores together side by side, as mentionedabove. In this case, it is preferred to have such a construction thatthe optical fiber cores can be regulated not only in vertical movementsbut also in lateral movements. As an example of such a construction, onehaving a shaping groove of a rectangular shape in cross-section asmentioned above can be mentioned.

In the present invention, the shaping jig is required to be movablevertically and laterally relative to the optical fiber cores. Itsoperation can be effected manually. To precisely form a coating on theoptical fiber tape core, however, it is more preferred to use a machinethat performs the coating mechanically or automatically. As a means formoving the shaping jig in the direction of the axes of the optical fibercores, any means can be used insofar as it can move the shaping jig at aconstant speed in the direction of a single axis. It is, however,preferred to use such a means that can start and stop the shaping jig atdesired positions and can also change its moving speed. For example, amoving system with the shaping jig secured on a 1-axis controlled robotcan be used. With the moving system, the moving position and movingspeed can be controlled.

To more precisely control the shape of a tape or the position of coreparts to be formed into a tape, it is preferred to use a system that cancontrol both of the feed rate of the coating material and the speed of arelative movement of the shaping jig. The use of such a system makes itpossible to fabricate an optical fiber tape core different in shape atpart or parts thereof or to increase the width and thickness of a tapeat position or positions, where strength, protection or the like isneeded, by changing the feed rate of the coating material or the speedof a relative movement of the shaping jig in the course of the formationinto the tape. To more strictly control the shape of the tape or theposition of core parts to be formed into the tape, it is preferred touse such a system that can also control the distance of a relativemovement of the shaping jig in addition to the above-described controlof the feed rate of the coating material and the speed of the relativemovement of the shaping jig.

Further, the shaping jig can be one that allows to change the height ofthe shaping jig in the course of its movement in the direction of theaxis of the optical fibers. Such a shaping jig makes it possible tofabricate an optical fiber tape core different in thickness or the likeat part or parts thereof by changing its thickness or shape in thecourse of fabrication. More preferred is a system that permits automatedmovements of the shaping jig in the vertical direction.

For the feeding of the coating material, any means can be used. Thefeeding can be conducted manually, although mechanical or automatedfeeding is preferred from the viewpoint of control. For example, it ispreferred that the initiation and termination of the feeding can beautomatically controlled at desired positions. From the standpoint ofimproving the yield of coating layers made of silicone rubber andcontrolling the shape such as thickness, it is also preferred to controlthe feed rate.

The fourth embodiment of the process of the present invention for thefabrication of an optical fiber tape core will next be described withreference to the drawings. As shown in FIG. 14, the fourth embodimentfirstly comprises arranging plural optical fiber cores (four opticalfiber cores in the diagrams) in alignment with each other on a substrate5 having a two-dimensional flat surface and applying a coating material3 onto the two-dimensional flat surface of the substrate such that theseoptical fiber cores 2 a-2 d are coated in a desired range (FIG. 14( a)).The plural optical fiber cores are next peeled off from the substratewhile holding them at uncoated end portions thereof (FIG. 14( b)). Atthis time, between parts of a coating layer made of silicone rubber,said parts being located on side walls of the outermost optical fibercores 2 a, 2 d, and a part of the coating layer, said part being locatedon the substrate, the coating layer is caused to fracture and separatealong the direction of the axes of the optical fiber cores so that acoated optical fiber tape core 1 is formed (FIG. 14( c)).

According to the above-described fourth embodiment, it is only necessaryto simply mount the optical fiber cores in alignment with each other onthe two-dimensional flat surface and to apply the coating material overthe optical fiber cores. It is, therefore, unnecessary to subject theoptical fiber cores to two-dimensional alignment upon conducting thecoating operation. Even if the number of cores is increased, an opticalfiber tape core can still be fabricated stably without development ofdimensional variations in the direction of the thickness of the opticalfiber cores. The range of coating is not limited and, even when coatingover a very short distance is desired, it is only necessary to simplyapply the coating material to the surfaces of the optical fiber cores.Accordingly, the formation of connector-equipped optical fiber coresinto a tape and the fabrication of a short-distance optical fiber tapecore can be performed with ease.

In the above-described fourth embodiment, the step in which thetwo-dimensional flat surface is coated with silicone rubber requiresonly to apply the silicone rubber such that a silicone rubber coatinglayer is formed at a constant thickness over the surface of the opticalfiber cores, and no limitations whatsoever are imposed on the manner ofthe coating. For example, plural optical fiber cores arranged on atwo-dimensional flat surface of a substrate can be coated with a coatingmaterial in advance. A shaping jig with its bottom wall formed into aflat surface can then be moved from a coating start position to acoating end position such that the silicone rubber on the surfaces ofthe optical fiber cores can be shaped into a uniform thickness by thebottom wall of the shaping jig. This manner makes it possible to applysilicone rubber at a more uniform thickness. The thickness of thesilicone rubber can also be controlled to a desired value by adjustingthe height of the shaping jig. Further, the coating material can bespread over the two-dimensional flat surface of the substrate with theoptical fiber cores arranged thereon by applying the coating materialthick over the optical fiber cores beforehand and then moving theshaping jig. In addition, the application of the coating material andthe movement of the shaping jig can be interlocked with each other.Furthermore, the coating and the shaping can be conducted at the sametime by using a jig that can perform coating and shaping at the sametime.

In the step that the plural optical fibers are peeled off from thetwo-dimensional flat surface, it is only necessary to set the movingspeed and moving direction and the angle between the optical fiber coresand the substrate at the time of the peeling such that the peeling canbe performed without deforming the shape of the coating layer, andtherefore, no particular limitation is imposed on the manner of thepeeling. For keeping the shape of the coating layer constant, however,it is preferred to control the moving speed constant during the peeling.

In the fourth embodiment, an optical fiber tape core maybe fabricated bycoating the surfaces of plural optical fiber cores with silicone rubberas described above and then peeling some of the optical fiber cores. Asillustrated in FIG. 15, for example, a coating material 3 is applied toa two-dimensional flat surface of a substrate 5 with plural opticalfiber cores 2 a-2 h mounted thereon such that the surfaces of theoptical fiber cores are coated (FIG. 15( a)). Subsequently, some 2 a, 2b of the optical fiber cores may then be peeled off from thetwo-dimensional flat surface to form an optical fiber core 1. Theoptical fiber cores 2 c,2 d may then be peeled off to fabricate anotheroptical fiber tape core (FIGS. 15( b) and 15(c)).

The coated silicone rubber may be cured or dried as needed. Thisprocessing can be conducted either before or after peeling the opticalfiber cores form the two-dimensional flat surface. These optical fibercores may also be peeled off while the curing or drying is beingconducted. In other words, the curing or drying processing can beconducted in any stage where the alignment of the optical fiber cores isnot affected.

In the above-described fourth embodiment of the present invention, thecoating of the optical fiber tape core may have a multilayerconstruction. FIG. 16 illustrates the fabrication of an optical fibertape core having a coating of a two-layer construction. After opticalfiber tape cores 1 a, 1 b fabricated by one of the first to fourthembodiments are arranged on a two-dimensional flat surface (FIG. 16(a)), a coating material 3 is applied over the optical fiber tape cores(FIG. 16( b)). By moving a shaping jig 7 in the direction of an arrow,the coating material on the surfaces of the optical fiber cores isshaped into a uniform thickness (FIG. 16( c)). These optical fiber tapecores are then peeled off from the two-dimensional flat surface. As aresult, an optical fiber tape core 1 having a coating layer of atwo-layer construction is formed (FIG. 16( d)).

In the above-described first to fourth embodiments of the process of thepresent invention for the fabrication of an optical fiber tape core, anadhesive layer may be arranged on each two-dimensional flat surface.When optical fiber cores are mounted on the two-dimensional flatsurface, they are temporarily held in place by the adhesive layer. Theoptical fiber cores, therefore, no longer require any positioning foralignment upon conducting coating or shaping so that the setting of theoptical fiber cores can be easily conducted in a shorter time. In thefourth embodiment, the existence of the adhesive layer has led togreater adhesive force to the coating material so that the coating layerhas been facilitated to fracture and separate along the direction of theaxes of the optical fiber cores, thereby making it possible to improvethe yield of products. In addition, it has also been facilitated toadjust the pitch intervals of the individual optical fiber cores.

Any adhesive can be used as an adhesive for use in the adhesive layer,insofar as it has adhesive force of such a degree as maintaining theshape of the optical fiber cores, keeping the optical fiber cores freefrom stress or strain and causing no damage on the optical fiber coresupon peeling them off. Usable examples of the adhesive can includevarious pressure-sensitive adhesives (adhesives) of the urethane,acrylic, epoxy, nylon, phenol, polyimide, vinyl, silicone, rubber,fluorinated epoxy and fluorinated acrylic types; thermoplasticadhesives, and thermosetting adhesives. From the ease in wiring theoptical fire cores, pressure-sensitive adhesives thermoplastic adhesivescan be used preferably. Any method can be used to bond the pluraloptical fiber cores on the adhesive layer. An automated wiring machinecapable of bonding the optical fiber cores to the adhesive layer underconstant pressure is also usable. A property can be imparted to theadhesive layer such that the adhesive layer is deactivated when thepeeling is conducted. The peeling of the optical fiber cores form theadhesive layer can be facilitated, for example, by applying a solvent orirradiating light.

In the first to fourth embodiments, the substrate may be provided in thetwo-dimensional flat surface thereof with a groove for bringing opticalfiber cores into alignment with each other. FIG. 17 illustrates aprocedure for fabricating an optical fiber tape core by using agroove-provided substrate in the fabrication process according to thefourth embodiment. On a substrate 5 having a two-dimensional flatsurface, a groove 5 a is arranged to bring optical fiber cores intoalignment with each other, and plural optical fiber cores 2 a-2 d arearranged in the groove (FIG. 17( a)). A coating material 3 is thenapplied and, if desired, a silicone rubber coating layer is shaped by asimilar shaping jig as those described in the above (FIG. 17( b)).Subsequently, the optical fiber cores are peeled off from the substrate(FIG. 17( c)), so that a coated optical fiber tape core 1 is formed(FIG. 17( d)). This procedure makes it possible to regulate lateralmovements of the plural optical fiber cores and to align and fix them bysimply placing the optical fiber cores in the groove in thetwo-dimensional flat surface. It is, therefore, possible to more easilycoat the plural optical fiber cores without spaces between them in analigned state and to more readily shape the resulting coating layer.

The groove in the two-dimensional flat surface is required merely topermit aligning optical fiber cores and holding them in place, so thatthe width and depth of the groove can be dimensioned in conformity withthose in the specification of an optical fiber tape core to befabricated. Further, no particular limitation is imposed on thecross-sectional shape of the groove, and no problem or inconveniencearises with a groove in the form of a V letter or a series ofsemicircles instead of a rectangular shape.

It is to be noted that the expression “to bring optical fiber cores intoalignment” as used herein means to arrange individual optical fibercores side by side at a desired position. The spaces between theindividual optical fiber cores may or may not be equal to each other,and can be set as needed depending upon the specification of an opticalfiber tape core of an optical fiber tape core to be fabricated.Concerning the coating of optical fiber cores, no particular limitationis imposed on a range in which the optical fiber cores are to be coated,insofar as the optical fiber cores are coated with silicone rubber atthe surfaces of at least parts of the optical fiber cores to be formedinto a tape. It is also possible to mount plural bundles of opticalfiber cores in parallel with each other and then to coat the bundles ofoptical fiber cores at the same time. Further, the expression “to peeloff optical fiber cores” means that the optical fiber cores and theirassociated two-dimensional flat surface are caused to separate relativeto each other, and the peeling-off of optical fiber cores can beeffected by moving either the optical fiber cores or the two-dimensionalflat surface. In the present invention, the individual optical fibercores arranged in alignment with each other on a two-dimensional flatsurface are required only that at least parts of them are arranged inalignment with each other on the same flat surface, and may includeparts where the optical fiber cores are intersecting. In addition, noparticular limitation is imposed on the number of optical fiber cores tobe coated all together. It is, therefore, possible to fabricate 2-coretape cores, 4-core tape cores, 6-core tape cores, 8-core tape cores,16-core tape cores, and so on.

EXAMPLES

The present invention will hereinafter be described more specificallybased on examples and comparative examples. It should, however, be bonein mind that the present invention shall by no means limited to thefollowing examples.

Examples 1-6 & Comparative Example 1

Each 8-core optical fiber tape core, which had such a construction asshown in FIG. 2( b) and was provided with a coating layer formed ofsilicone rubber, was obtained by arranging, as optical fiber cores,eight single-mode optical fibers of 250 μm outer diameter and 125 μmcladding diameter at 250 μm pitches in parallel with each other,applying to one sides of the optical fibers a coating formulation of thecorresponding silicone rubber shown in Table 1, and then curing thesilicone rubber under the corresponding curing conditions also shown inTable 1. The application of the coating formulation of the siliconerubber was conducted following the procedure of Example 7 to bedescribed subsequently herein.

TABLE 1 Silicone rubber Tensile Material in coating Hardness strengthCuring No. formulation Company name [−] [kgf/cm²] conditions 1 “SE9186L”Dow Corning Toray 24 15 Room Silicone temperature 2 “KE106” Shin-EtsuSilicones 56 80 100° C./0.5 h 3 “KE66” Shin-Etsu Silicones 40 15 Roomtemperature 4 “SE4410” Dow Corning Toray 85 64 150° C./0.5 h Silicone 5“TSE3380” GE Toshiba Silicones 70 25 150° C./0.5 h 6 “TSE3281-G” GEToshiba Silicones 84 45 150° C./1 h

With respect to the thus-obtained optical fiber tape cores, thefollowing tests were then conducted.

(Single-Core Separability Test)

Work was conducted on each optical fiber tape core (500 mm) to separateit into single optical fiber cores, and the ease of the work was ranked.

(Twist Property Test)

Each optical tape core (100 mm) was pulled under tension of 300 gf and,after the optical tape core was twisted 10 times or 20 times at one endthereof, the external appearance of the optical tape core was ranked.Specifically, the optical tape core was observed under a microscope fordamages such as cleavage and coating layer peeling.

(Curl Property Test)

Each optical tape core (380 mm) was wound 2 full turns on a bobbin of 60mm diameter. After the optical tape core was left over for 1 hour, theoptical tape core was unwound and then, the degrees of its curling atboth ends from a flat table surface were determined.

The test results so obtained are shown in Table 2.

TABLE 2 Material Single-core Twisting test Curling No. separability 10times 20 times test [mm] Evaluation Example 1 1 Good No damage No damage≦1 mm Acceptable Example 2 2 Good No damage No damage ≦1 mm AcceptableExample 3 3 Good No damage No damage ≦1 mm Acceptable Example 4 4 GoodNo damage No damage ≦1 mm Acceptable Example 5 5 Good No damage Nodamage ≦1 mm Acceptable Example 6 6 Good No damage No damage ≦1 mmAcceptable Comp. Ex. 1 * Good Fractures in — 100 mm Unacceptable coatinglayer * Optical fiber tape core making use of a UV curable resin(“8-CORE TAPE S′08/8T”, product of The Furukawa Electric Co., Ltd.)

As shown in Table 2, the optical fiber tape cores of Invention Examples1-6 showed excellent single-core separability and exhibited sufficienttensile strength, and had been resolved to the maximum extent in theproblem of development of curling due to the retention of a wound shape.

In the optical fiber tape core of Comparative Example 1, on the otherhand, the single-core separability was good, but the strength was notsufficient and curling had been developed as a result of the winding.

An 8-core optical fiber tape core having the construction shown in FIG.3( b) was also fabricated and evaluated likewise, and similar results asshown in Table 2 were obtained.

Example 7

Using four optical fiber cores 2 a-2 d of 25 cm length (products of TheFurukawa Electric Co., Ltd., quartz-based single-mode optical fibers,outer diameter: 0.25 mm), an optical fiber tape core of 20 cm length,0.4 mm thickness and 1.1 mm width was fabricated by the coating machineshown in FIG. 18.

The used coating machine was constructed of a 1-axis controlled robotand a coating material feeder for feeding a coating material to anozzle. The 1-axis controlled robot had a flat substrate 10 for mountingoptical fibers thereon. A ball screw shaft 11 was arranged along thelongitudinal direction, is provided at an end thereof with a drive motor14, and is supported at an opposite end thereof by a journal bearing 15.A movable unit 12 is arranged in threaded engagement with the ballscrew, and is provided with a nozzle 4 such that the nozzle extendsperpendicularly to the stage surface. On the movable unit, the nozzlewas constructed such that it was movable not only in the verticaldirection but also in the longitudinal direction and was fixable at apredetermined position. Further, a flexible pipe 8 was connected to thenozzle to feed the coating material from a coating material feeder 13.As the nozzle 4, a dispenser needle made of stainless steel (outerdiameter: 1.2 mm, inner diameter: 0.9 mm) was used.

Firstly, the four optical fiber cores were aligned in parallel with eachother on the substrate 10 along a line on which the movable unit of the1-axis controlled robot 9 was movable, and at opposite end parts towhich no coating was to be applied, were held in place by adhesive tapes6 such that the same tension was applied to the individual optical fibercores. As a coating material, a thermosetting silicone rubber resinhaving a hardness of 84 and a tensile strength of 45 gf/cm²(“TSE3281-G”, product of GE Toshiba Silicones) was used. As the coatingmaterial feeder 13 for feeding the coating material to the nozzle, adispenser was used.

The movable unit 12 of the 1-axis controlled robot 9 was next controlledto move the nozzle 4 to a coating start position A for the aligned fouroptical fiber cores (FIG. 18( a)). The movable unit 12 of the 1-axiscontrolled robot 9 was adjusted such that the center of the nozzle wasbrought into registration with the center of the four optical fibercores, and the clearance between the optical fiber cores and the freeend of the nozzle 4 was set at 0.15 mm.

Next, the moving speed of the movable unit 12 of the 1-axis controlledrobot 9 and the delivery pressure of the coating material feeder 13 wereset at 50 mm/sec and 5.0 kg/cm², respectively. Concurrently with theinitiation of a movement of the nozzle 4, a delivery of the coatingmaterial 3 was initiated. By moving the nozzle 4 in the direction of theaxes of the optical fibers, the coating material was applied onto theoptical fiber cores (FIG. 18( b)). When the nozzle 4 had moved to acoating end position B, the delivery of the coating material was stopped(FIG. 18( c)). Subsequently, the optical fiber tape core was treatedunder the conditions of 150° C. for 1 hour to effect the curing of thecoating material.

By coating and curing the coating material through the above operation,it was possible to apply the coating over the surfaces of the pluraloptical fibers all together. The thus-obtained optical fiber tape corewas good in single-core separability, was not peeled off when twisted 10times, and did not develop curling.

According to the above procedure, it was possible to fabricate opticalfiber tape cores of 1.1 mm and less in width and 0.4 mm and less inthickness without developing any problem. Since it was possible todeliver the coating material only as much as needed to coat by movingthe nozzle while delivering the coating material under constantpressure, the yield was good so that the cost of the coating materialwas successfully reduced.

Example 8

An optical fiber tape core was fabricated in a similar manner as inExample 7 except that the moving speed was changed to 35 mm/sec in arange of 10 cm at central parts of the optical fibers. In the resultingoptical fiber tape core, the width and thickness of its central partwere 1.2 mm and 0.55 mm, respectively, and were greater than those ofthe remaining parts (width: 1 mm, thickness: 0.4 mm). The optical fibertape core was good in single-core separability, was not peeled off whentwisted 10 times, and did not develop curling. The optical fiber tapecore was provided with increased strength, did not undergo breakage evenwhen bent severely, and therefore, had sufficient strength.

Example 9

Provided were four optical fiber cores of 25 cm length with MUconnectors attached to one ends thereof. The four optical fiber coreswith the MU connectors attached to the one ends thereof were formed attheir central parts of 15 cm into a tape in a similar manner as inExample 7.

According to the above procedure, the optical fiber tape core wassuccessfully fabricated at the predetermined position of the opticalfiber cores with the MU connectors attached to the one ends thereof. Bythe formation into the tape, the optical fibers were united together andwere increased in strength. The optical fibers, therefore, showed betterhandling ease in a system, leading to an improvement in workability.

Example 10

To fabricate an optical fiber tape core of 60 cm length, 1.1 mm widthand 0.4 mm thickness by using four optical fiber cores of 80 cm length(products of The Furukawa Electric Co., Ltd., quartz-based single-modeoptical fibers, outer diameter: 0.25 mm), the procedure shown in theflow diagrams of FIG. 9 were practiced. It is, however, to be noted thatmovements of a shaping jig were conducted manually. Employed as theshaping jig was one having a size of 40 mm in width (L), 30 mm in length(S) and 40 mm in height (H) and provided at a laterally central partthereof with a shaping groove having a size of 1.1 mm in width (W) and0.4 mm in height (h). As a coating material, a thermosetting siliconerubber resin having a hardness of 84 and a tensile strength of 45kgf/cm² (“TSE3281-G”, product of GE Toshiba Silicones Co., Ltd.) wasused.

Firstly, the four optical fiber cores 2 a-2 d were aligned in parallelwith each other on the substrate 5 in the optical fiber tape corefabrication facilities, and at their opposite end portions to which nocoating was to be applied, were held in place by adhesive tapes 6. Thecoating material was then applied to the surfaces of the four opticalfiber cores over a range of 60 cm where the optical fiber cores were tobe formed into a tape, and the surface of the coating material waslightly leveled by a spatula (FIG. 9( a)).

Next, the shaping jig 7 was placed on the substrate such that the fouroptical fiber cores were located in the shaping grove 7 a of the shapingjig (FIG. 9( b)). The shaping jig was then moved in the direction of theaxes of the optical fibers from the coating start position A to thecoating end position B (FIG. 9( c) and FIG. 9( d)). Subsequently, thethus-shaped coating material was cured under the conditions of 150° C.and 1 hour to fabricate a 4-core optical fiber tape core. Thethus-obtained optical fiber tape core was good in single-coreseparability, was not peeled off when twisted 10 times, and did notdevelop curling.

In this example, the setting of the optical fiber cores required merelyto bring the optical fiber cores, which had been mounted on thesubstrate, into the shaping groove of the shaping jig. Accordingly, thetime required for the work was short and the operations were simple,resulting in improved working efficiency. Further, the thus-obtainedoptical fiber tape core was 1.2 mm in tape width and 0.35 mm inthickness, that is, was substantially of the preset dimensions, and thetape shape was substantially semielliptic in cross-section as desired.

Example 11

Using four optical fiber cores of 90 cm length (products of The FurukawaElectric Co., Ltd., quartz-based single-mode optical fibers, outerdiameter: 0.25 mm), an optical fiber tape core of 70 cm length, 1.1 mmwidth and 0.4 mm thickness was fabricated by the fabrication steps shownin FIG. 19. A coating machine employed in the fabrication was of theconstruction illustrated in FIG. 19. Described specifically, the coatingmachine was constructed of a flat substrate 10 for mounting the opticalfiber cores thereon, said flat substrate being provided with a side, a1-axis controlled robot 9 having a ball screw shaft 11 provided at oneend thereof with a drive motor 14 and at an opposite end thereof with ajournal bearing 15, and a coating material feeder 13 capable ofcontrolling the feed rate of a coating material. The drive motor andjournal bearing are fixedly secured on the side wall, and a shaping jig7 was arranged on a movable unit 12, which was maintained in threadedengagement with the ball screw shaft 11, such that the shaping jig wasmovable in a vertical direction relative to the substrate. Accordingly,the shaping jig was movable in the vertical and longitudinal directionsby the movable unit 12. In this example, a dispenser was used as thecoating material feeder 13, and as the coating material, a thermosettingsilicone rubber resin having a hardness of 84 and a tensile strength of45 kgf/cm² (“TSE3281-G”, product of GE Toshiba Silicones Co., Ltd.) wasused.

A shaping jig employed in this example had the same size as that used inExample 10, but at its free end part (on the forward side as viewed inthe moving direction of the shaping jig), was provided with a circularthrough-hole having a diameter of 2 mm and extending to a shapinggroove. A flexible pipe 8 is connected to the through-hole such that thecoating material can be fed from the coating material feeder 13.

Firstly, the four optical fiber cores 2 a-2 d were aligned in parallelwith each other on the flat substrate 10, and at their opposite endportions to which no coating was to be applied, were held in place byadhesive tapes 6. Next, the movable unit 12 was moved such that thethrough-hole of the shaping jig 7 was located at the coating startposition A (FIG. 19( a)). The shaping jig 7 was then lowered such thatthe four optical fibers are located in the shaping groove of the shapingjig (FIG. 19( b)). While feeding the coating material, the shaping jigwas moved at a speed of 50 mm/sec in the direction of the axes of theoptical fiber cores (FIG. 19( c)). When the through-hole of the shapingjig had reached the coating end position B, the feeding of the coatingmaterial was terminated and further, the shaping jig was moved tocomplete the coating and shaping work (FIG. 19( d)). Subsequently, thethus-shaped coating material was cured under the conditions of 150° C.and 1 hour to fabricate a 4-core optical fiber tape core. Thethus-obtained optical fiber tape core was good in single-coreseparability, was not peeled off when twisted 10 times, and did notdevelop curling.

In this example, the setting of the optical fiber cores required merelyto bring the optical fiber cores, which had mounted on the substrate,into the shaping groove of the shaping jig. Accordingly, the timerequired for the work was short and the operations were simple,resulting in improved working efficiency. By providing the shaping jigwith the shaping groove and the through-hole and feeding the coatingmaterial, it was possible to perform both the coating and the shaping atthe same time by the shaping jig of the very simple construction.Moreover, the feed rate of the coating material was controllable so thatthe coating material was not fed excessively, leading to an improvementin material yield. In addition, it was possible to coat, that is, toform a tape only at a predetermined position. Therefore, thethus-obtained optical fiber tape core was 1.1 mm in tape width and 0.4mm in thickness, that is, was substantially of the preset dimensions,and the tape shape was substantially semielliptic in cross-section asdesired.

Example 12

Using four optical fiber cores of 35 cm length (products of The FurukawaElectric Co., Ltd., quartz-based single-mode optical fibers, outerdiameter: 0.25 mm), an optical fiber tape core of 25 cm length, 1.1 mmwidth and 0.4 mm thickness was fabricated by the fabrication steps shownin FIG. 20. A coating machine employed in the fabrication was the sameas that used in Example 11, but as the shaping jig 7, was used oneprovided at a laterally central part thereof with a rectangular shapinggroove of 1.1 mm width and 0.4 mm height and at a longitudinally centralpart of the shaping groove with a through-hole of 2 mm diameter. Exceptfor the shaping jig, the 4-core optical fiber tape core was fabricatedin a similar manner as in Example 11.

In this example, the setting of the optical fiber cores required merelyto bring the optical fiber cores, which had mounted on the flatsubstrate, into the shaping groove of the shaping jig. Accordingly, thetime required for the work was short and the operations were simple,resulting in improved working efficiency. By arranging the through holeat the longitudinal center of the shaping groove formed in the shapingjig and feeding a coating material, it was possible to perform both thecoating and the shaping at the same time by the shaping jig of the verysimple construction while aligning the optical fibers. As it wasunnecessary to align the optical fibers together and in parallel witheach other, a further improvement was achieved in working efficiencywith respect to the setting of the optical fibers. Moreover, the feedrate of the coating material was controllable so that the coatingmaterial was not fed excessively, leading to an improvement in materialyield. In addition, it was possible to coat, that is, to form a tapeonly at a predetermined position. Therefore, the thus-obtained opticalfiber tape core was 1.1 mm in tape width and 0.4 mm in thickness, thatis, was substantially of the preset dimensions, and the tape shape wassubstantially rectangular in cross-section as desired. The thus-obtainedoptical fiber tape core was good in single-core separability, was notpeeled off when twisted 10 times, and did not develop curling.

Example 13

Using four optical fiber cores of 40 cm length (products of The FurukawaElectric Co., Ltd., quartz-based single-mode optical fibers, outerdiameter: 0.25 mm), an optical fiber tape core of 30 cm length wasfabricated. A coating machine employed in this example was of theconstruction illustrated in FIG. 21. Described specifically, the coatingmachine was constructed of a flat base 10 with a substrate 5 arrangedthereon to permit mounting the optical fiber cores, and a 1-axiscontrolled robot 9 having a ball screw shaft 11 provided at one endthereof with a drive motor 14 and at an opposite end thereof with ajournal bearing 15. A shaping jig 7 had a size of 40 mm width, 30 mmlength and 40 mm height, had a flat surface at the bottom wall thereof,and was arranged in a direction vertical to the substrate on a movableunit 12 mounted on a ball screw shaft 11. Accordingly, the movable unit12 was able to move the shaping jig in the vertical and longitudinaldirections. It is to be noted that coating of a coating material andmovements of relative to the substrate for the optical fiber cores wereconducted manually. As the coating material, a room-temperature curablesilicone rubber having a hardness of 24 and a tensile strength of 15kgf/cm² (“SE9186L”, product of Dow Corning Toray Silicone Co., Ltd.) wasused.

Firstly, the four optical fiber cores 2 a-2 d were aligned in parallelwith each other on the substrate 5, and at their opposite end portionsto which no coating was to be applied, were held in place by adhesivetapes 6, so that they were arranged above the flat base 10 (FIG. 21(a)). Next, the coating material 3 was applied to the surfaces of thefour optical fiber cores in a range of 30 cm where the optical fibercores were to be formed into a tape. The movable unit 12 was then movedsuch that the bottom wall of the shaping jig 7 was located at a heightof 0.1 mm from the surfaces of the four optical fiber cores, and wasmoved at a moving speed of 50 mm/sec in the direction of the axes of theoptical fiber cores (an arrow mark) (FIG. 21( b)). The thus-shapedcoating material was then semi-cured under the conditions of roomtemperature and a curing time of 30 minutes. Next, the optical fibercores were held at one ends thereof by a hand and then pulled in anupper direction, so that the optical fiber cores were peeled off fromthe substrate (FIG. 21( c)). The thus-obtained optical fiber tape corewas treated further under the conditions of room temperature and 1 hourto completely cure the coating material, so that the 4-core opticalfiber tape core was obtained. The thus-obtained optical fiber tape corewas good in single-core separability, was not peeled off when twisted 10times, and did not develop curling.

The above-described procedure allowed to perform the shaping of theoptical fiber tape cores very easily, and therefore, was able to makethe fabrication time shorter than the conventional fabricationprocesses. Further, it was unnecessary to conduct any two-dimensionalalignment adjustment. Therefore, optical fiber tape cores werefabricated without wasting, and the yields of the optical fiber coresand coating material were good. Moreover, the thus-obtained opticalfiber tape cores had a uniform thickness of 0.35 mm.

Example 14

A 30-cm long, 8-core optical fiber tape core of a unitary 2-layerconstruction was fabricated by using two of the optical fiber tape coresfabricated in Example 13, arranging the optical fiber tape cores side byside in parallel with each other, coating the optical fiber tape corestogether with a thermosetting silicone rubber having a hardness of 84and a tensile strength of 45 kgf/cm² (“TSE3281-G”, product of GE ToshibaSilicones Co., Ltd.). As a shaping machine and forming jig, the samemachine and jig as those employed in Example 13.

Firstly, two optical fiber tape cores obtained in a similar manner as inExample 13 were arranged in parallel with each other on a substrate.Next, the coating material was applied to the surfaces of the twooptical fiber tape cores. A movable unit was then moved such that abottom wall of a shaping jig was located at a height of 0.05 mm from thesurfaces of the two optical fiber tape cores, and was moved at a movingspeed of 50 mm/sec in the direction of the axes of the optical fibercores. The thus-shaped coating material was then semi-cured under theconditions of a curing temperature of 150° C. and a curing time of 30minutes. Next, the optical fiber cores were held at one ends thereof bya hand and then pulled in an upper direction, so that the optical fibercores were peeled off from the substrate. The thus-obtained, 8-coreoptical fiber tape core was treated further under the conditions of 150°C. and 1 hour to completely cure the coating material, so that the8-core optical fiber tape core of the two-layer construction wasobtained. The thus-obtained optical fiber tape core was good insingle-core separability, was not peeled off when twisted 10 times, anddid not develop curling.

In the above-described example, the optical fiber tape core of thetwo-layer construction was successfully fabricated the same facilitiesand procedure as in Example 13. Unlike the conventional processes, itwas unnecessary to replace the jig for use in the fabrication. Thefabrication was, therefore, possible with good working efficiency and atlow cost. The thus-obtained optical fiber tape core had a uniformthickness of 0.4 mm.

Example 15

Using four optical fiber cores of 40 cm length, an optical fiber tapecore was fabricated in a similar manner as in Example 13 except for theuse of a substrate equipped with a groove which was 0.1 mm in depth and1.1 mm in width and had a rectangular shape in cross-section. As thealignment of the optical fiber cores was successfully achieved by simplymounting the optical fiber cores in the groove, the setting of theoptical fiber cores was feasible without any precise positionalalignment. Accordingly, it was possible to shorten the time required forthe work. It was also possible to conduct the work with ease, resultingin improved working efficiency.

Example 16

Using four optical fiber cores of 40 cm length provided at opposite endsthereof with MT connectors, an MT-connector-equipped, 4-core opticalfiber tape core was fabricated by forming them into a tape at theircentral parts of 35 cm length. As a substrate having a two-dimensionalflat surface, a polyimide film of 500 mm×100 mm in size and 125 μm inthickness was used, and on one side of the substrate, an adhesive layerof 100 μm in film thickness was formed. The four optical fiber coreswere bonded on the adhesive layer of the substrate such that they wereheld in place in alignment with each other. Subsequently, the procedureof Example 13 was followed likewise to fabricate the 4-core opticalfiber tape core.

In this example, the optical fiber cores provided at the opposite endsthereof with the MT connectors was arranged and temporarily held inplace beforehand on the adhesive layer. It was, therefore, possible toconduct the application and shaping of the coating material easily anduniformly. It was also possible to conduct with ease the positionalalignment of the shaping jig. Accordingly, it was possible to shortenthe time required for the work, resulting in improved workingefficiency. Using the MT-connector-equipped optical fiber tape core, itsconnection to optical components in a system was performed. As theoptical fiber tape core had been formed into the tape at the centralpart thereof, it was possible to easily handle its optical fiber coresand to readily connect them to the optical components, resulting inimproved working efficiency.

INDUSTRIAL APPLICABILITY

The optical fiber tape core according to the present invention hasextremely good characteristics that it is equipped with bothsufficiently high strength and flexibility and hardly develops curling.Upon attachment of connectors or during installation work, its opticalfiber cores neither break nor develop curling, thereby bringing aboveimprovements in reliability, work safety and work efficiency. Accordingto the fabrication process of the present invention for the opticalfiber tape core, plural optical fiber cores can be readily formed intothe tape by coating them together at a desired position and shaping theresulting coating layer with a nozzle and forming jig of simpleconstructions.

1. A process for fabricating an optical fiber tape core by coatingplural optical fiber cores all together, wherein the optical fiber corecomprises an optical fiber core assembly with plural optical fiber corestwo-dimensionally arranged in parallel with each other, and a coatinglayer formed of silicone rubber and arranged on one side of said opticalfiber core assembly, said silicone rubber forming said coating layer;and said plural optical fiber cores do not intersect each other at anylocation along said plural optical fiber cores, the process comprisingthe steps of: mounting said optical fiber cores in alignment with eachother on a two-dimensional flat surface such that said optical fibercores do not intersect each other at any location along said pluraloptical fiber cores; applying silicone rubber onto said two-dimensionalflat surface such that said two-dimensional flat surface with saidplural optical fiber cores mounted therein is coated with said siliconerubber to form a coating layer; and peeling off said plural opticalfiber cores from said two-dimensional flat surface to separate, fromsaid coating layer on said two-dimensional flat surface, only a partthereof located on the peeled optical fiber cores.
 2. The processaccording to claim 1, wherein only some of said coated, plural opticalfiber cores are peeled off from said two-dimensional flat surface. 3.The process according to claim 1, wherein a coating layer formed ofsilicone rubber having a hardness of from 20 to 90 and a tensilestrength of from 15 to 80 kgf/cm2 is formed.
 4. The process according toclaim 1, wherein said two-dimensional flat surface is provided with anadhesive layer for temporarily holding said optical fibers in place onsaid two-dimensional flat surface.
 5. The process according to claim 1,wherein said two-dimensional flat surface is provided with a groove foraligning said optical fiber cores on said two-dimensional flat surface.